From one of the sources cited in the article: https://carnegieendowment.org/research/2024/06/ukraine-public-opinion-russia-war?lang=en

Many Ukrainians may be open to negotiations in theory, but they overwhelmingly did not trust Russia to negotiate in good faith. Most Ukrainians (86 percent) believed that there is a medium or high risk that Russia will attack again even if there is a signed peace treaty, and even more (91 percent) believed that Russia’s motive to enter negotiations is to take time to prepare for a new attack. Even among those who supported negotiations with Russia, only 21 percent believed that signing a peace treaty would help Ukraine deter future Russian aggression.

Putin's problem is he burned all the trust the world had in him when he attacked Ukraine after saying he would not. If he is truly serious about peace, he first needs to rebuild that trust.